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Formula: CaS
Sulphide, galena group
Specific gravity: 2.58
Hardness: 4
Colour: Pale brown to dark brown, colourless to pale brown in transmitted light, tarnishes strongly on exposure to
humid air (Mindat)
Common impurities: Mg,Na,Fe,Cu
Environments
Due to high melting point of 2450oC, oldhamite is an early nebular condensate;
it may fill the latest interstices between silicates in enstatite chondrite and achondrite
meteorites. Associated minerals include
enstatite, augite,
niningerite, osbornite,
gypsum, calcite and
troilite
(HOM).
Terrestrial oldhamite is associated with pyrometamorpism, especially with coal fires. It is quite unstable in air, and
hydrolysis makes it change into portlandite. It also occurs in anthropogenic blast
furnace slag
(Mindat).
Localities
At the type locality, the Bustee meteorite, Gorakhpur, Basti District, Uttar Pradesh, India, oldhamite occurs as
single-crystal nodules, to 3 mm, in an enstatite chondrite
meteorite. Associated minerals include
troilite, osbornite,
niningerite, gypsum,
enstatite, calcite and
augite
(Mindat).
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